House Training
When I first heard about crating my puppy I thought it was cruel, but after witnessing it first hand I have changed my mind 100%. Crating is keeping your dog in a small enclosed area, usually made of wire cage or as in my dogs case a travel carrier donated to me by some good friends - Mark & Jennie Farra after their Rottweiler Zeus out grew it.
Crating should not be done for several hours until your puppy is at least 6 months old. To get your dog used to being left alone in the crate, I put my puppy in the travel carrier and stayed with him for a few minutes then letting him out - as soon as he was let out he was given praise and a treat. The amount of time was slowly increased. Eventually I would leave the room for a few minutes, upon returning I would let him out and give him a treat.
Unfortunately if your pre-six month old puppy starts to go to the bathroom in the house - about the only thing to do is: when he starts, carry him outside to finish. Upon completion outside praise him. Eventually he will start to get the idea.
When the dog reaches about six months old I recommend crating him or her. Dogs are clean animals, they will not soil his den where they sleep. Thus by keeping your puppy in a small area he will learn to hold it until released to the outside.